All assessments levied under this act shall be a first and prior lien, subject only to state and county taxes and assessments based on any irrigation bond issue outstanding at the time of the passage of section [sections] 50-1801 through 50-1835[, Idaho Code], against the property assessed from and after the first Monday of April of any year, and such lien shall not be removed until the assessments are paid or the property sold for the payment thereof, and any lots, pieces or parcels of real estate within the boundaries of such city irrigation system owned by a city or county and not used purely for governmental purposes shall be subject to such assessment.